Question

我有一个结构为

的表格

Table 3

Fruit ID -  Foreign Key  (Primary Key of Table 1)
Crate ID -  Foreign Key  (Primary Key of Table 2)

现在我需要执行一个查询，

更新 Crate ID Fruit ID 如果 Fruit ID 已在表格中，如果没有，则将表3中的记录作为新记录插入。

这就是我现在在代码中得到的，

private void RelateFuirtWithCrates(List<string> selectedFruitIDs, int selectedCrateID)
{

   string insertStatement = "INSERT INTO Fruit_Crate(FruitID, CrateID) Values " +
        "(@FruitID, @CrateID);";  ?? I don't think if it's right query

        using (SqlConnection connection = new SqlConnection(ConnectionString()))
        using (SqlCommand cmd = new SqlCommand(insertStatement, connection))
        {
            connection.Open();
            cmd.Parameters.Add(new SqlParameter("@FruitID", ????? Not sure what goes in here));
            cmd.Parameters.Add(new SqlParameter("@CrateID",selectedCrateID));        
}

Answer 1

您可以使用SQL Server中的MERGE语法执行“upsert”：

MERGE [SomeTable] AS target
USING (SELECT @FruitID, @CrateID) AS source (FruitID, CrateID)
ON (target.FruitID = source.FruitID)
WHEN MATCHED THEN 
    UPDATE SET CrateID = source.CrateID
WHEN NOT MATCHED THEN   
    INSERT (FruitID, CrateID)
    VALUES (source.FruitID, source.CrateID);

否则，您可以使用以下内容：

update [SomeTable] set CrateID = @CrateID where FruitID = @FruitID
if @@rowcount = 0
    insert [SomeTable] (FruitID, CrateID) values (@FruitID, @CrateID)

我该如何更新SQL表逻辑

1 个答案: